Twierdza Osowiec - Fort IV Nowy in Goniądz

You're standing at Osowiec Fortress, a nineteenth-century stronghold in north-eastern Poland. Take a look around. The fortress is surrounded by marshes and bogs along the river Biebrza. That's no accident. This was the one place where you could actually cross the marshland, so whoever held this spot controlled the passage. The railway from Białystok to Königsberg also ran straight through the fortress and crossed the river right here.